Steam Methane Reforming plants have the ability to produce pure hydrogen, as well as CO or combinations or mixtures thereof. For environmental reasons or other economical drivers, it is becoming more and more important in new projects to include plans to be capture-ready and include a CO2 capture solution. This is also the case for hydrogen production plants such as SMR plants.
US-A-2012/0121497A describes a solution for efficient capture of CO2 from an SMR plant:                Use of a High Temperature shift followed by a Low Temperature Shift        Separation of the shifted syngas through a Pressure Swing Adsorption (PSA)        Compression of the PSA off-gas        Separation of CO2 through a sub ambient temperature purification unit (CPU)        Use of two sets of membranes to recycle part of the hydrogen to the PSA and part of the CO2 to the cryogenic purification unit        
Separation in a PSA to remove hydrogen followed by compression and subambiant temperature separation is described in EP-A-1869385.
Traditionally, when a CO co-production is required in a project, CO is produced from the synthesis gas before the high temperature shift, as described in U.S. Pat. No. 4,861,351. In a case with CO production and CO2 capture, the obvious solution would be to have one part of the syngas treated before shift by the CO cold box and the other part treated through two sets of shifts (HT Shift followed by LT Shift) and to have the CPU located on the PSA off gas.